Graphical instrument



a 1959 KOUNG-SHIN LEE 2,867,906

I GRAPHICAL INSTRUMENT Filed Nov. 1.' 1954 I I 0% H l .9 1 .1 z I 20 17/5 Figu g 33 -2G /2 INVENTOR Koung Shin Lee BY 24 W 9% A 7'7'ORNEYSF/gur 2 United States Patent GRAPHICAL INSTRUMENT Koung-Shin Lee, ForestHills, N. Y.

Application November 1, 1954, Serial No. 466,032

1 Claim. (Cl. 33-93) This invention relates to a graphical instrumentfor use in mechanical drawing and related applications where it isdesired to construct lines at various slopes and angles relative to areference edge.

The principal object of this invention is to provide a draftinginstrument which gives simultaneous indications of the slope and theangle of a line relative to a reference edge.

Another object is to provide a drafting instrument which will solvegraphically various trigonometric problems.

A further object is to provide a drafting instrument which is acombination triangle and trigonometric calculator.

An additional object is to provide a drafting instrument which can beused to construct a line at any angle or slope in any of the fouranalytical geometric quadrants.

Other objects and advantages will become apparent in the followingdescription and accompanying drawings wherein:

Fig. 1 is a plan view of the graphical instrument, showing the straightedge in a partially extended position in dotted lines and in its closedposition in solid lines; and

Fig. 2 is a plan view of the graphical instrument showing two variationsin its manner of use on a drawing board.

Referring to the drawings, Fig. 1 shows the graphical instrument of thepresent invention, generally designated by the numeral 10. Theinstrument has a right triangular base plate 11 with one acute-angledcorner portion 12 rounded off as shown. Overlying the base plate 11 is asectoral frame 13 which has a curved portion 14 and two straight sides15, 16 extending from opposite ends 17, 18 of the curved portion to meetat an offset vertex 19.

Sectoral frame 13 is rotatably attached at the vertex 19 to the baseplate 11 by means of a pivot 20 located near the rounded-off cornerportion 12 thereof so that the frame can be rotated to differentoverlying positions relative to the base plate 11, for example, as shownby the dotted lines in Fig. 1.

Attached along one side 16 of the frame 13 is a straight edge member 21which extends in length beyond curved portion 14 of the frame 13 to formwith its outer edge 22, in conjunction with the base plate 11, thehypotenuse of an isosceles right triangle when the frame is in the fullyoverlying, or closed position relative to the base plate, as shown bythe solid lines in Fig. 1. In such position the inner edge 23 of thestraight edge member 21 bears against the hypotenuse edge 24 of the baseplate, thereby limiting the counterclockwise movement of the framerelative to the base plate as viewed in Fig. 1. The pivoted end 25 ofthe straight edge member 21 terminates short of the pivot so that themember may be rotated to a position perpendicular relative to the baseside or reference edge 26 of the base plate 11 when the latter is beingmaintained in contact with a straight edge or the like.

Curved portion 14 has an arcuate slot 27 along its length through whicha setor clamping-screw 28 is attachable to base plate 11. The screw 28when loosely attached to base plate 11 rides in the slot 27, permittinga freedom of rotation for the frame 13 relative to the base plate. Thescrew may be manually tightened to clamp the frame in a fixed positionrelative to the plate.

The outer edge 29 of the curved portion 14 of frame 13 has angularindicia or a protractor scale 30 marked off on it in appropriategraduations of degrees. Adjacent the rotational path of the latter edgeis an arrow or index mark 31 marked into the base plate which indicateson the protractor scale 30 the angular setting of the outer edge 22 ofthe straight edge 21 relative to the reference edge 26 of the baseplate.

Also located on the base plate 11 is a graph-ruled area 32 which is inthe shape of an isosceles right triangle having its hypotenuse 33parallel to the reference edge 26 of base plate 11 and substantiallyaligned with the inner or index edge 34 of lower side 15 of the sectoralframe 13 when the latter is in its closed position as viewed in Fig. 1.The right angle vertex 35 of the ruled area is adjacent to hypotenuseedge 24 of the base plate 11 and one acute angled vertex 36' thereof islocated at pivot 20.

The two sides 37, 38 of the ruled area are each marked off in evenlyspaced decimal graduations of equal valuev by means of indicia or scales39, 40. Likewise index edge 34 of sectoral frame 13 is marked off insimilar units with indicia or scale 41. The preferred major graduationson sides 37, 38 run from 0 to 10 and on index edge 34 from 0 toapproximately 14 in the manner as shown in Fig. 1. Minor graduations 42may be chosen for convenience.

The basic feature of this instrument is the isosceles right triangulargraph-ruled area 32 on the base plate 11 and the index edge 34 on thesectoral frame. Together wtih the 45 protractor scale 30 on curvedportion 14 of the sectoral frame 13, a straight line of any slope orangle can be constructed by setting straight edge 21 at the desiredposition relative to reference edge 26 of base plate 11.

For example, if it is desired to draw a straight line with a slope of10/6, the instrument should be adjusted to the position indicated by thedotted lines in Fig. 1, namely, so that index edge 34 of sectoral frame13 intersects scale 40 of the ruled area 32 at the major graduation 6.Thus a line drawn coincident with straight edge member 21 will have aslope of 10/6 relative to a line drawn coincident with reference edge26. The angle between the two lines (approximately 59") may be read offin degrees on protractor scale 30 at index mark 31.

It is apparent that at any particular setting of the index edge 34relative to the ruled area 32, the three sides and included angles of aplurality of similar right triangles are immediately determinable. Theprotractor scale 30 may be marked in degrees and complementary degrees,so that for the above setting the acute angles could be read to be 31and 59.

The lengths of the respective sides can be read directly if either oneof the two sides or the hypotenuse is known. Thus if the longer side is5.5 units, such 5.5 units will be read along scale 39. Then read from5.5 on scale 39 along the line parallel to scale 40 (see dotted arrow A)until such line meets index edge 34, and read from that point along theline parallel to scale 39 (see dotted arrow B) until scale 44) along theside 38 is reached. Thus it is determined that the shorter side is 3.3units. The point of meeting the index edge marks off on said edge thelength of the hypotenuse, in this case about 6.4 units.

Similarly for other lengths of longer sides of a 31"- 5990 triangle readoff on scale 39 of ruled area 32, the shorter sides and respectivehypotenuses can be read off on scale 40 of the ruled area 32 and theindex edge 34 of sectoral frame 13 respectively.

In addition, for the complement of the angle at which the straight edgemember 21 is set relative to the reference edge 26, the tangent of suchcomplementary angle can can beread ofi on scale 39. Thusthisinstrumentcan be used to graphically-solve various-trigonometric prob lems. v

For example, for the setting shown by the dotted lines in-Fig. -1,thertangentof approximately 31 (the'complement-of-the setting'of 59canbe read off-on scale 40: as .60. Likewisethe sine of -suchcomplementaryyangle of3 1- isindicated from the on index edge 34" to be.52 on scale 40 (see dotted arrow C), and the'cosineis read as .86 onscale 39 (see arrow'D)-.:

As shown'in Fig. 2, the isosceles character ofthebase plate- 11 providesmany versatile positions and edgesfor constructing similar triangles forone setting of the'instrument. Such versatility is' helpful forconstructing lines in the various geometric quadrants.

For example, when constructing linesat angles greater than 135 in thesecond quadrant, the straight edge is placed against a perpendicularreference (such as another triangle) and the desired line is drawncoincident with the reference edge 26 of the instrument. Thus toconstruct-a line at an angle of 150, set the straight edge atan angle of60 relative to the reference edge, then placing the straight edgeperpendicular to a T-square'ori base line, thereferenceedge'of theinstrument will form an angle of 30 with said base line, permittingconstruetion of the line at 150 in the second quadrant.

This instrument-may be constructed of any suitablema changes may be madein its construction andarrange-- ment of parts without departing fromthe inventive conceptand the scope of the following claim.

What I claim is:

A drafting instrument comprising a 45 right isosceles triangular baseplate, a sectoral frame having a curved portion and two straight sidesdisposed at 45 relative to one another and meeting at a vertex, saidframe pivotally attached at said vertex to a corner portion of one ofthe acute angles of said base plate in overlying relation to r the sameto provide an axis of "rotation for said frame relative tosaid/base,L.a-i straight edgemember attached along one of said sides ofsaid frame, said member movable into limiting' conta'ct alongits'lengthwith the'hypotenuse 'of said baseplate; a-ismallerl similarz4 5? rightisosceles triangular graph-ruled area on said base plate having one ofits-acute'angledwertices located at said axis and having its hypotenusedisposed parallel to the equal side of said base plate adjacent saidaxis, and the equal side of the area coincident with said axis disposedparallel to thehypptenuseof said baseplate, ,decimalindicia markedalongtheequal sides of said'area,- corre-' sponding indicia marked alongthe-other of said sides of, said frame, angular indicia along saidcurved portion. ofsaid frame marked ofl in actual andcomplementaryydegrees, and an-index mark on said base plate adjacenttherotational path of saidcurved portion of" said :frame to indicate onsaid angular indicia the angular setting of saidz straight edge relativeto saidequal side of said base plate adjacent said axis.

7 References Citedin the file of thlSipatellt UNITED STATES PATENTS-29,767 Chisholm Aug; 28, 1860 378,257 Leschorn- Feb; 21,1888; 662,977-SchmelZ Decr 4,,1900- 888,173 Justice May 19, 1908;

1,003,857 Adams- Sept; 19, 1911 1,056,206 Norman Mar. 18, 1913;:2,154,753 Kallio Apr. 18,,1939; 2,412,901: McCoshen Dec..17, 1946FOREIGN" PATENTS 355,856 Great Britain Sept. 3, 1931 838,653- GermanyMay 12,.1952;

